It is known to use nonwoven fiber mats made with glass fibers and bonded with aqueous thermosetting resins, like urea formaldehyde or phenolic resole resins to make molded parts and laminates. It is also known to use a nonwoven fiber glass mat to laminate to polymeric foam such as polystyrene foam to act as stiffeners and stabilizers in the manufacture of automotive parts such as automobile head liners, as disclosed in U.S. Pat. No. 4,729,917. Products produced with foam laminates having one or two layers of nonwoven fiber glass mat with urea formaldehyde binder are affected by high humidity and high ambient temperature to cause an unpleasant odor and also to deteriorate the binder strength. Also, non-extendible mat, i.e. a mat bound with a resin binder that is fully cured, is relatively stiff and does not conform well to curves and complex curvature, such as three dimensional curvature, and still provide excellent rigidity or stiffness to the foam laminate.
It is also known to make nonwoven fiber glass mats by chopping dry strands of glass fibers bound together with a binder to form chopped strand, to collect the chopped strand on a moving conveyor in a random pattern, and to bond the chopped strand together at their crossings by dusting a dry, powdered thermoplastic binder like a polyamide, polyester or ethylene vinyl acetate on wetted chopped strands followed by drying and curing the binder, as disclosed in U.S. Pat. No. 5,565,049. While such mat products are very useful including bonding to a layer of polymeric foam to stiffen the foam, these mats do not have as high a tensile strength as desired, and as achieved with a wet laid nonwoven fiber glass mat, because the bundles or chopped strands in the mat, according to the invention of the above cited patent, do not bond together as well as the individual fibers in a typical nonwoven mat.
For example, the average sum of the machine direction tensile and the cross machine direction tensile for a chopped fiber glass strand mat made in this manner and having a basis weight of about 1.88 pounds per 100 sq. ft. is about 24 lbs. per 3 inch width compared to at least twice this tensile for wet laid nonwoven fiber glass mats. Mats made according to the above patented process also are more expensive to make than a typical nonwoven mat made with known wet laid processes.
It is also known to make a nonwoven fiber glass mat bonded with “B” staged acrylic resin having a glass transition temperature above 45 degrees C. and to use such mats to form a laminate with a foam layer for use in automotive head liners as disclosed in U.S. Pat. No. 6,008,147, but this mat is not well suited for laminating to a polymeric fibrous web when the desired shape contains complex curvatures requiring the mat to stretch substantially during molding. Further, it is known to use an acrylic copolymer latex, such as a self-crosslinking acrylic copolymer of an anionic emulsifying type as one component of at least a two component binder for bonding glass fibers and particulate thermoplastic to make a glass fiber reinforced sheet that can later be hot molded into various shapes and articles, as disclosed in U.S. Pat. No. 5,393,379.
Finally, it is known to make stampable, moldable, sheets of fiber glass reinforced thermoplastic by forming a dilute aqueous slurry containing glass fibers and thermoplastic particles or thermosetting particles smaller than 1 millimeter in size and passing the slurry through a moving forming screen to form the sheet and drying the sheet at a temperature high enough to bond the plastic particles together while retaining the particulate shape of the plastic particles, as disclosed in European Patent Specification 148,760. A conventional aqueous binder is applied to the wet formed mat of fibers and plastic particles when a mat intended for cutting and press molding is made. The added aqueous binder provides the strength in the dry mat needed to withstand handling in the cutting and press molding operations.
European Patent Application 148,761 and U.S. Pat. No. 4,690,860 also teach similar methods and mats as taught by European Patent Specification 148,760. U.S. Pat. No. 4,690,860 teaches inpregnating a stampable sheet containing glass fibers and a thermoplastic binder with a liquid thermosetting plastics material like liquid phenol formaldehyde or liquid melamine formaldehyde resin and then molding the sheet at elevated temperature and pressure to form a molded product that retains its hardness over a wider range of temperatures. This reference also suggests using powdered thermosetting resins like those used for in-mold coating of known art, but does not suggest forming a fibrous non-woven containing a novolac resin bonding the crossing fibers together throughout the mat. Sheets or mats made according to these disclosures are not sufficiently rigid or heat and sag, resistant for certain applications like automotive headliners because they contain a 40-60 percent of thermoplastic material and do not have a thermosetting matrix throughout the mat.